Piston



ne 24, 1952 A. TOWNHILL PISTON 2 Sl-IEETS--SHEET 1 Filed Sept. 10, 1949 A. TOWNHILL June 24, 1952 PISTON Filed Sept. 10, 1949 Patentecl June 24, 1952 PISTON Arthur Townhill, Cleveland, Ohio, assignor to Thompson Products, Inc., Cleveland, Ohio, a.

corporation of Ohio Application September 10, 1949, Serial No. 115,091

12 Claims. 1

This invention relates to a piston having skirts on opposite sides of the fire ring groove or ring flange thereof.

Specifically, this invention relates to Very short trunk-type pistons for internal combustion engines which are held against tilting by the addition of a skirt in the position conventionally occupied by the ring grooves.

The conventional trunk type piston has a head with a depending ring flange and a skirt. The head end of the piston, being composed of solid metal such as aluminum or the like, had to be fitted rather loosely in the operating cylinder and clearances of more than .007 to .010 inch per inch have been necessary. To lessen tilting tendencies in such a piston, it was necessary to provide a rather long skirt, or to fit the skirt very tightly in the cylinder. Since tilting produces piston slap and allows the piston rings to tilt, it must be minimized for efficient operation and many skirt designs have been proposed for this purpose. In the prior known skirt designs, however, elimination of tilting tendencies were always attempted by lengthening the skirt or increasing the tightness of the skirt.

The present invention now eliminates the necessity for long or tight-fitting piston skirts. According to this invention, the head end portion of the piston is provided with a skirt to coact with a skirt at the opposite end of the piston. The ring grooves are positioned between these skirts. Both skirts are made flexible through the use of slots, splits, thin sections, and the like. If desired, the skirt at the head end of the piston can be provided with a belt or band for controlling expansion. In addition, both skirts are preferably ground in an elliptical shape with their major axes at right angles to the axis of the pin bosses.

It is, then, an object of this invention to provide a piston with a cross head or guide skirt at the head end thereof in advance of the ring grooves for coacting with a skirt at the other end portion of the piston to minimize tilting tendencies.

Another object of the invention is to provide a piston for internal combustion engines and the like which has skirts at opposite ends thereof.

Another object of the invention is to provide a piston with a flexible skirt at the portion thereof that is normally used for the ring grooves.

A still further object of the invention is to provide a trunk-type piston having a head and a depending skirt and ring flange but equipped With flexible skirt portions in advance of the ring flange and surrounding the head.

A still further object of the invention is to provide a short piston for internal combustion engines which has opposite end portions of larger diameter than the intermediate portion and 2 wherein the intermediate portion has ring grooves therein.

Other and further objects of the invention will be apparent to those skilled in the art from the following detailed description of the annexed sheets of drawings which, by way of preferred examples only, illustrate two embodiments of the invention.

On the drawings:

Figure 1 is a side elevational view of a piston according to this invention.

Figure 2 is a top plan view of the piston shown in Figure 1.

Figure 3 is a vertical cross-sectional view taken along the line IIIIII of Figure 2. r

Figure 4 is a vertical cross-sectional View taken along the line IVIV of Figure 2.

Figure 5 is a bottom plan view of the piston of Figures 1 to 4.

Figure 6 is a diagrammatic view showing the relative shapes ofithe head end of the piston and a cylinder in which it operates.

Figure '7 is a fragmentary side elevational view of the head end of a modified piston according to this invention. 1

Figure 8 is a top plan View of the modified piston of Figure 7.

Figure 9 is a vertical cross-sectional view taken along the line IX-IX of Figure 8.

As shown on the drawings:

The piston 10 of Figures 1 to 5 inclusive has a body with a head II, a hollow depending ring flange or side Wall portion i2, and a depending skirt [3 at the end of the portion 12. The ring flange portion 12 has diametrically opposed pin bosses M, It having their inner extensions reinforced by ribs i5, [5 which diverge into the head I. A transverse head reinforcing rib It extends diametrically across the under side of the head II in parallel relation to the axis of the pin bosses. Ring grooves l! are formed around the ring flange l2, two being shown, although any number could be provided. Thickened beads l3, l8 are formed around the inner face of the end of the ring flange l2 under the piston bosses I4, l4 and merge into the under faces of these piston bosses as at 18a. These beads l8, l8 as shown in Figure 5, extend more than 45 on each side of the pin boss axis and do not extend around the bearing faces of the pistons which are normal to the pin boss axis.

An oil ring groove [9 is formed around the ring flange I2 at the bottom end thereof and extends into the bosses [8. Since the beads l8,

7 l8 are spaced apart at the bearing face sides of the piston, the ring groove l9 will have an open inner face between the beads as shown in Figure 4.

The skirt I 3 as best shown in Figure l is of larger diameter than the side wall or flange por- 3 tion [2 and slots 20, 20 are formed around the bearing face side of the flange l2 just beneath the oil ring groove I9. These slots 20 terminate at thickened lug portions 200, on the inner face of'the piston. The thickened lugs reinforce the weakened wall created by the slots 20 and minimize the tendency of cracking the unslotted por tion of the wall at this level. The slots 20 extend for at least about 45 on each side of the bearing face axis of the piston which is normal to the pin boss axis.

In accordance with this invention, the head H has a skirt 2! therearound in advance of the ring flange I2. This skirt is of larger diameter than the ring flange I2 and is rendered flexible on the bearing face sides of the piston by arcuate slots 22 cut through the head to a peripheral groove 23 just above the top fire ring groove [1. As shown in Figure 2, these slots extend for at least about 45 on each side of the center line of the bearing faces of the piston.

As shown in Figure 6, the skirt 2| is ground to an oval shape with its major axis normal to the pin boss axis so that the skirt will have flexibility in the cylinder C and can maintain a good bearing engagement around the bearing faces of the assembly without being forced into an undesired tight frictional fit. The skirt can expand across its minor axis without materially increasing the bearing load on the bearing faces thereof.

The skirt I3 is also oval ground to the same dimensions as the skirt 2| and therefore has its bearing faces arranged in the same manner as the bearing faces of the skirt 2!). The slots 20 and 22 for the skirts l3 and 2| respectively render these skirts quite flexible so that undue binding in the cylinder will not occur even when the piston appreciably expands under the influence of excessive heat.

In the modified piston 30 of Figures 7 to 9, parts identical with parts described in Figures 1 to 6 have been designated with the same reference numerals. In the modified piston 30, however, the head end skirt 2| has a vertical split 3| across one bearing face thereof and a metal band 32 is imbedded in the skirt and extends across this split. The band 32 is a ring of metal having a coeificient of expansion less than the metal forming the skirt. The ring is integrally cast into the skirt and, as shown in Figures 8 and 9, is outwardly of the slot 22. The band is effective to control expansion of the skirt. The piston 30 is otherwise identical with the piston II).

From the above descriptions, it will be understood that this invention now provides a piston for internal combustion engines and the like with a cross head or guide skirt in advance of the ring grooves and cooperating with a second skirt at the opposite end of the piston. The skirt portions are of larger diameter than the main side wall or ring groove portion of the piston and are separated from this portion by slots which extend around the bearing face sides of the piston so that these skirts, in effect, are only connected to the ring flange or main body of the piston at the end boss sides thereof. The skirts are preferably oval ground and one or more of them can carry an expansion control ring. The skirts can have good bearing fit with the cylinder at the major axis portions thereof without binding against the cylinder even when excessively heated since the skirts are flexible and will expand across the minor axis. Clearances of about .0015 inch 4 or less are practical at the bearing faces of the skirts while at the pin boss portions of the skirts these clearances can be .015 inch or more, giving a ten-to-one ratio for accommodating expansion. Such bearing fits were heretofore impossible at the head end of a piston because the prior art pistons had to be equipped with a solid head.

Since the skirts at the opposite ends of the pistons of this invention will effectively hold the piston against tilting, the invention has made possible efficient operating short pistons.

It 'will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

1. A trunk type piston having a body portion, skirts at both ends of said body portion and spaced therefrom, and ring grooves between the skirts.

2. A piston comprising a head, a depending ring flange, and skirts at opposite ends of the ring flange and spaced therefrom.

3. A piston comprising a head, a depending ring flange, and skirts at both ends of the ring flange having larger diameters than the ring flange and spaced therefrom, each of said skirts having a non-circular periphery with bearing faces at the ends of the major axes thereof.

4. A piston comprising a body having a head, a depending ring flange, and pin bosses on the ring flange, the improvement of skirts of larger diameter than the ring flange at both ends of the ring flange and connected to the ring flange on the pin boss sides only of the piston.

5. A piston comprising a body having ahead at one end thereof and a hollow cylindrical body depending from said head, said body having a reduced diameter portion intermediate the ends thereof, ring grooves formed around the periphery of said reduced diameter portion, piston pin bosses on said reduced diameter portion, opposed arcuate slots separating the end of the body opposite the head from the reduced diameter portion around the sides of the body that is normal to the pin boss axis, said body having a peripheral groove therearound in advance of the ring grooves, and opposed arcuate slots in the head of the piston extending from the top end face thereof to said peripheral groove around the sides of the body normal to the pin boss axis to separate flexible skirt portions from the head whereby said skirt portions will cooperate with the opposite end of the piston to prevent tilting of the 7 piston.

6. A piston for an internal combustion engine comprising a body having a head, a hollow side wall, pin bosses carried by the side wall, and skirts at the ends of the side wall, one of said skirts surrounding said head and being separated therefrom at localized arcuate portions, the other of said skirts depending from the side wall and being separated therefrom by localized slots, said skirts being connected to the head and side wall respectively only on the wrist pin boss side of the piston.

7. A non-tipping short trunk type piston for internal combustion engines and the lik which comprises a hollow cylindrical body having a solid head end, a skirt'surrounding said solid head end and locally separated therefrom, and said skirt having a larger major diameter than the side wall of the piston.

8. A piston comprising a head, a hollow cylinder body depending from the head, opposed pin bosses on said body, ring grooves around the body, a peripheral groove around the body in advance of the ring grooves and adjacent said head, a first skirt of larger diameter than the body surrounding said head, opposed arcuate slots between the head and first skirt extending around the non-pin boss sides of the piston from the top of the head to said peripheral groove whereby said first skirt is connected to the piston only through localized portions which are axially aligned with the pin bosses, a second skirt depending from the end of said body and having a larger diameter than said body, said second skirt being at a level beneath the pin bosses and locally separated from the body by opposed arcuate slots extending around the non-pin boss sides of the body, and said first and second skirts having a non-circular configuration with a major axis normal to the pin boss axis. 1

9. In a piston, the improvement of a head having a surrounding skirt, and. a second skirt at the end of the piston opposite said head.

10. In a piston of the type including a head, a hollow cylindrical body carrying pin bosses, and ring grooves around the body, the improvement which comprises a skirt surrounding said head in advance of said ring grooves, and a second skirt attached to and spaced from the end of said body opposite said head.

11. A piston comprising a hollow cylinder having a head at one end thereof, spaced opposed skirts at both ends thereof, one of said skirts surrounding said head and both of the skirts being of larger diameter than the body, said body having opposed thickened bead portions adjacent the skirt at the end opposite said head, a peripheral groove around the body extending into said thickened bead portions and through the body between the bead portions, pin bosses on the body above said peripheral groove, and ring grooves in the body between the pin bosses and the skirt surrounding the head.

12. A piston comprising a hollow cylindrical body having a head at one end thereof, a first skirt surrounding said head and connected thereto at opposed localized sides thereof, a second skirt depending from the opposite end of the body and connected thereto at opposed localized portions, said first and second skirts being of larger diameter than the body and eilective to prevent tilting of the body, and pin bosses on the body between the skirts.

ARTHUR TOWNHILL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,222,413 King Apr. 10, 1917 2,130,923 Jardine Sept. 20, 1938 2,193,920 Frederick Mar. 19, 1940 2,240,640 Ducate May 6, 1941 FOREIGN PATENTS Number Country Date 701,093 France July 15, 1980 

